Use of fetal pulse oximetry during labor

Fetal surveillance during labor is mainly based on fetal heart rate monitoring in France. In case of abnormal FHR, fetal scalp blood analysis may reduce the rate of cesarean section. Fetal pulse oximetry, a recent second-line technique of fetal monitoring could also reduce obstetrical interventions. Several maternity departments in France and other European countries are currently using this new tool routinely. Several observation studies have shown the potential interest of pulse oximetry. Randomized controlled trials will soon be able to conclude on the real benefits that can be expected from pulse oximetry during therm labor in normally grown fetuses. Other clinical situations such as meconium-stained amniotic fluid, preterm labor or fetal growth retardation remain to be explored.     

A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE: Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate patterns in labor improves the accuracy of fetal assessment and allows safe reduction of cesarean deliveries performed because of nonreassuring fetal status. STUDY DESIGN: A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the combination of electronic fetal monitoring and continuous fetal pulse oximetry (study group). The primary outcome was a reduction in cesarean deliveries for nonreassuring fetal status as a measure of improved accuracy of assessment of fetal oxygenation. RESULTS: A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4. 5%; vs. control, 10.2%; P =.007). However, there was no net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs. control, 130 [26%]; P = .49) because of an increase in cesarean deliveries performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dystocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassuring fetal status, there was an improvement in both the sensitivity and the specificity for the study group compared with the control group for the end points of metabolic acidosis and need for resuscitation. CONCLUSION: The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. However, the addition of fetal pulse oximetry did not result in an overall reduction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability to more appropriately intervene by cesarean or operative vaginal delivery for fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and remains to be explained.     

Fetal pulse oximetry: from the first experimental studies of broad clinical use. An assessment of current status

Pulse oximetry has triggered a revolutionary change in monitoring patients in many branches of medicine. For 4 years fetal sensors with specially calibrated pulse oximeters are tested clinically. Additional examination methods are required for accurate monitoring the fetus intrapartum because of the low specificity of cardiotocographs and also to avoid unnecessary operative deliveries. Research on hand up to now has demonstrated that fetal pulse oximetry is a method easy to learn, easily applicable and well quanitifiable to improve fetal monitoring and the interpretation of the fetal heart rate patterns intrapartum. Prospective intervention studies involving management studies still have to prove the clinical value of this new technology. Only after examining a large number of hypoxic-risk fetuses we can assess whether pulse oximetry in a management can replace invasive fetal blood analysis as a continuous, non-invasive method of monitoring. Various teams try to prove a context between arterial saturation values (SpO2) and biochemical changes of the fetus in connection with a crucial limiting value of 30% by correlating changes of the fetal scalp with the oxygen saturation. Guidelines for the assessment of the SpO2-values are established according to the present level of knowledge and future aspects of the method are examined.     

Fetal scalp blood sampling for pH and lactate measurement during labour

The wide use of continuous of fetal heart rate monitoring (FHR) since the seventies has been accompanied by an increase in cesarean delivery rates, without any decrease in cerebral palsy rate. Second line methods of fetal monitoring have been developed in order to better identify fetuses truly at risk of intrapartum asphyxia. The use of fetal scalp blood sampling (FBS) for fetal monitoring seems logical since neonatal acidosis is one of the major criteria of birth asphyxia. Studies show that the use of FBS reduces the increase in cesarean deliveries associated with the use of continuous FHR monitoring. However, FBS is invasive, non continuous and technically uneasy, with a rather high rate of failed blood samplings. Fetal scalp lactates measurement by micromethod requires a much smaller volume of blood. Although a wider assessment is required, the predictive value of fetal blood lactates seems to be similar to that of fetal scalp blood pH.     

Clinical usefulness of pulse oximetry in the fetus with non-reassuring heart rate pattern?

The objective of this study was the evaluation of intrapartum pulse oximetry as an indicator of fetal distress and the condition of the newborn during clinical routine surveillance in an University Perinatal Center. Between 1998 and 1999 pulse oximetry (SpO2) was used additionally to routine fetal monitoring by electronic fetal heart rate tracing (CTG) and fetal blood sampling (FBA) in 128 cases with nonreassuring heart rate pattern. Cut off values were FIGO Score < 8 for the heart rate pattern and for fetal blood sampling during labor results of < 7.25 (preacidosis). The condition of the newborn was defined by the APGAR score with the cut off < 7 at 1 minute, while the biochemical status was evaluated by means of arterial blood sampling of the umbilical artery directly after birth using a pH of < 7.20 to verify acidosis. Predictive values of critically low SpO2 values (< 30%) for at least 10 minutes as well as corresponding sensitivities and specificities were calculated together with 95% confidence intervals to identify fetal distress or a depressed condition of the newborns. Of 128 fetuses included in this study 66 (52%) were born spontaneously, 23 (18%) were born by operative vaginal delivery and 39 (31%) by means of cesarean section. The high rate of cesarean section was due to cephalopelvic disproportion in 29 cases. Fetal outcome was evaluated with a clinical score: mean APGAR score value 8.5 SD +/- 1. The mean value of the pH in the umbilical artery was 7.23 +/- 0.04. During a SpO2 monitoring period of 18,381 minutes we analyzed a contact time of 63%. Comparing SpO2 values of < 30% with preacidosis in the fetal blood sampling, we found a positive predictive value of merely 0.17 (95% CI: 0.00-0.64). Of 9 preacidotic cases during delivery only 1 was indicated by a saturation value below 30% (sensitivity 0.11, 95% CI: 0.00-0.48). The specificity and negative predictive value were calculated as 0.83 (95% CI: 0.65-0.94) and 0.76 (95% CI: 0.58-0.89) respectively. Of eleven cases with acidosis in the blood of the umbilical cord artery, pH < 7.20, only 2 were indicated by a SpO2 values below 30%. Which is equivalent to a sensitivity of 0.18 (95% CI: 0.03-0.52). Results of a receiver operator curve analysis showed no substantial deviation from the diagonal. The area under the curve was 0.62, the 95% CI (0.47-0.76) indicating no significant discrimination. Three of 49 fetuses with SpO2 recording during the last 10 minutes were born in clinical depressed status (APGAR < 7). None was indicated by a SpO2 value below 30%. CONCLUSION: Fetal distress and impaired condition of the newborn are not identified or predicted during routine application of SpO2 monitoring in the fetus during labor with adequate safety.     

Fetal pulse oximetry and wavelet analysis of the fetal heart rate in the evaluation of abnormal cardiotocography tracings

AIM: Previous studies indicate that the addition of wavelet analysis of the fetal pulse oximetry tracings (FSPO2) and fetal heart rate (FHR) variability to cardiotocography (CTG), for intrapartum fetal monitoring, provides useful information on the fetal response to hypoxia. We applied the new procedure in non-reassuring CTG patterns, in which cesarean section was performed, and tested its accuracy in the diagnosis of the intrapartum fetal compromise. METHODS: At the 'Aretaieion' University Hospital labor ward, 318 women with term fetuses in the cephalic presentation entered the trial during labor. They all were monitored with external CTG and fetal pulse oximetry. In the cases that cesarean section was applied, because of abnormal CTG tracings, we applied a method based on the multiresolution wavelet analysis and a self-organized map neural network on the first and second stage of labor. The main outcome parameter was the rate of cord metabolic acidosis at birth (pH < 7.05). Secondary outcomes included Apgar scores at 5 min, fetal transmission to neonatal intensive care unit (NICU) and neonatal encephalopathy. RESULTS: Fifty out of 318 cases delivered operatively because of abnormal CTG patterns (rate 15.72%). In 30 cases, cord pH was >7.05, while in 11 Apgar scores at 5 min were <7, while none of those neonates were transferred to NICU. In the rest 20 cases cord pH was <7.05; in all of these cases Apgar scores at 5 min were <7, while four neonates were transferred to NICU. In one of them, neonatal encephalopathy was diagnosed. After the offline application of wavelet analysis and neural networks to the pulse oximetry and FHR variability readings of the 50 cases, statistics calculated that the system showed a sensitivity of 85% and a specificity of 93%, while false negative and false positive rates were 15% and 7%, respectively. CONCLUSION: Computerized FHR and FSPO2 monitoring shows an excellent efficacy and reliability in interpreting non-reassuring FHR recordings.     

Effect of maternal epidural analgesia on fetal intrapartum oxygen saturation

The use of maternal epidural analgesia in labor may be associated with nonreassuring fetal heart rate (FHR) patterns. Fetal oxygen saturation (FSpO2) monitoring may improve assessment of fetal well-being during this time. Mean FSpO2 values were compared over seven 5-minute epochs: 5 minutes prior to an epidural event (combined insertion of epidural/top-up epidural analgesia and infusion pump bolus), to 30 minutes following the event, including possible effects of maternal position and FHR pattern on FSpO2 values. Mean FSpO2 values were significantly different between the 5 minutes prior (49.5%) versus 16-20 minutes (44.3%, p <0.05), 21-25 minutes (43%, p <0.01), and 26-30 minutes (43.8%, p <0.05) epochs; and 6-10 minutes (48.3%) versus 21-25 minutes (43%, p <0.05) epochs, but were not influenced by FHR pattern or maternal position. There were no differences in mean FSpO2 values following administration of an epidural infusion bolus. We conclude that fetal oxygenation was affected following initial or top-up epidural analgesia and that fetal intrapartum pulse oximetry may be useful in assessing fetal status following these events.     

Evaluation of fetal heart rate patterns during the second stage of labor through fetal oximetry.

The purpose of this study was to assess the feasibility and accuracy of fetal pulse oximetry during the second stage of labor in cases with abnormal fetal heart rate (FHR) patterns with reference to postpartum acid-base status and Apgar scores. Forty-eight parturients with normal and 20 parturients with abnormal FHR tracings during the second stage of labor were monitored by fetal pulse oximetry and postpartum umbilical artery pH, pO(2), pCO(2) values and 1- and 5-min Apgar scores. The mean SpO(2) value was 55. 47 +/- 9.95% in cases with normal and 52.55 +/- 16.42% in cases with abnormal FHR patterns. A significant correlation was noted between fetal SpO(2) and umbilical artery pH in cases with normal (r = 0.76, p < 0.05) as well as in cases with abnormal FHR patterns (r = 0.78, p < 0.05). No significant correlation was found between fetal SpO(2) and Apgar scores at 1 and 5 min in cases with normal FHR patterns. On the contrary a significant correlation was noted in cases with abnormal FHR patterns. A normal FHR pattern alone is reassuring. In cases with abnormal FHR, fetal pulse oximetry is an objective method for distinguishing a hypoxic fetus.     

胎儿血氧饱和度监测的临床应用

胎儿脉冲血氧测定(fetal pulse oximetry,FPO)可提高产程中对胎儿健康状况评估的准确性。现有随机对照临床试验结果显示,它可以降低胎心宫缩监护(CTG)提示不确定胎儿情况的剖宫产率,但不会降低总体剖宫产率。     

Use of fetal pulse oximetry among high-risk women in labor: a randomized clinical trial

OBJECTIVE: The purpose of this study was to determine the clinical role of fetal pulse oximetry to reduce cesarean delivery for a nonreassuring fetal heart rate tracing. STUDY DESIGN: Singletons > or =28 weeks were randomized to fetal pulse oximetry plus electronic fetal heart rate monitoring (monitoring + fetal pulse oximetry) or monitoring alone. RESULTS: Overall, 360 women in labor were recruited: 150 cases with monitoring+fetal pulse oximetry and 177 cases with monitoring alone were analyzed. Most demographic, obstetric, and neonatal characteristics were similar. Specifically, the gestational age, cervical dilation, and station of the fetal head were not differential factors. In addition, cesarean delivery for nonreassuring fetal heart rate tracing was not different between the group with monitoring+fetal pulse oximetry (29%) and the group with monitoring alone (32%; relative risk, 0.95; 95% CI, 0.75, 1.22). Likewise, cesarean delivery for arrest disorder was similar between the group with monitoring+fetal pulse oximetry (22%) and the group with monitoring alone (23%; relative risk, 1.05; 95% CI, 0.79, 1.44). However, the decision-to-incision time was shorter for the group with monitoring+fetal pulse oximetry (17.8 +/- 8.2 min) than for the group with monitoring alone (27.7 +/- 13.9 min; P < .0001). CONCLUSION: The use of fetal pulse oximetry with electronic fetal heart rate monitoring does not decrease the rate of cesarean delivery, although it does alter the decision-to-incision time.     

Dystocia in nulliparous patients monitored with fetal pulse oximetry

OBJECTIVE: A critical analysis of the United States randomized controlled trial of fetal pulse oximetry concluded that nonreassuring fetal heart rate patterns used for study entry may have been a marker for dystocia. We prospectively studied nulliparous women in labor whose progress was monitored with fetal pulse oximetry to examine the relationship between nonreassuring fetal heart rate patterns and operative delivery for dystocia. STUDY DESIGN: A prospective nonrandomized observational cohort study compared two distinct classes of nonreassuring fetal heart rate patterns (class I: intermittent, mildly nonreassuring; class II: persistent, progressive, and moderate to severely nonreassuring) among nulliparous patients with the use of fetal pulse oximetry to confirm fetal well-being. Definitions of dystocia included the cessation of labor progress in the first (3 hours) or second (2 hours) stage of labor, despite adequate uterine activity that was assessed with an intrauterine pressure catheter. Independent review confirmed the classification of nonreassuring fetal heart rate patterns and study entry criteria. RESULTS: Two hundred seventy-four patients met study criteria and had sufficient information for fetal heart rate tracing interpretation. Two hundred thirty-seven patients (86.5%) were class II, and 37 patients (13.5%) were class I. The two classes of patients were comparable in a variety of obstetric, demographic, and perinatal variables. Twelve percent of all patients were delivered for nonreassuring fetal status. Significantly more class II patients (22%) were delivered by cesarean for dystocia than were class I patients (8%). Higher doses and a longer number of hours of oxytocin were required among class II patients. Significantly more occiput posterior positions were noted among all patients who underwent cesarean delivery for dystocia compared with other modes of delivery. CONCLUSION: Significantly nonreassuring fetal heart rate patterns predict cesarean delivery for dystocia among nulliparous patients with normally oxygenated fetuses in a setting of a standardized labor management protocol. This confirms the observations in the randomized controlled trial of fetal pulse oximetry in the United States and may provide insight into the treatment of nonprogressive labor in contemporary practice.     

Acute fetal distress

Three different clinical patterns of acute fetal distress may be observed during labor: an ante-partum hypoxia with a persistent nonreactive and "fixed" fetal heart rate (FHR) on admission to the hospital, a progressive intra-partum asphyxia manifested, as the labor continues, by a substantial rise in baseline heart rate, a loss of variability and repetitive severe variable or late decelerations, and finally, as a result of a catastrophic event, a sudden prolonged FHR deceleration to approximately 60 beats per minute lasting until delivery. However the majority of fetuses with nonreassuring tracings of FHR are neurologically intact, as evidenced by the high false-positive rate of electronic fetal monitoring (EFM). Therefore the diagnosis of fetal distress must be corroborated by complementary methods, such as continuous recording of the fetal electrocardiogram or computed-assisted EFM, fetal pulse oximetry or fetal scalp sampling with immediate determination of blood gases or lactates. Defavorable outcome of an acute fetal distress leading to neonatal encephalopathy or death is best predicted by a persisting low Apgar score (<3) for more than 5 minutes and by a severe metabolic acidosis (umbilical artery pH<7,00 and base-excess>-12mmol/l).     

Management of fetal distress.

Since its introduction more than 20 years ago, continuous electronic FHR monitoring has become the standard in most modern obstetric units. Practitioners well versed in FHR pattern interpretation do not question the value of fetal monitoring. Not only does this modality detect hypoxia early in its evolution, but also it allows the opportunity to understand the physiology of the hypoxia and to intervene if necessary. Although nonrandomized studies demonstrate an improvement in the perinatal death rate with continuous monitoring, most randomized studies have failed to confirm this observation. Continuous fetal monitoring has been associated in several studies with an increase in the CS rate; however, concomitant changes in obstetric practice have also raised the incidence of CS, making the interpretation of to what degree fetal monitoring is responsible for this increase difficult. Other than this association with an increased CS rate, fetal monitoring seems to present few risks. A thorough understanding of basic fetal heart abnormalities is crucial to prevent unnecessary intervention; however, although quite sensitive, FHR monitoring remains nonspecific in predicting fetal metabolic acidosis. Fetal pulse oximetry is a recent development still undergoing investigation. The ability to measure fetal oxygen saturation during labor adds critical information about fetal status and refines the interpretation of abnormal FHR patterns. If approved by the US Food and Drug Administration, it has the potential to affect dramatically the practice of obstetrics.     

Repérage de l’asphyxie au cours du travail

Intrapartum asphyxia is defined as metabolic acidemia measured at birth with pH < 7.00 and base deficit ≥ 12 mmol/L. It is today established that the proportion of cerebral palsy associated with intrapartum hypoxia-ischemia is about 14.5%. Intrapartum asphyxia is screened in France by the continuous fetal heart rate (FHR) monitoring which presents a good sensitivity for its detection. His low specificity justifies the use of second line methods to reduce the increase of cesarean deliveries associated with the use of continuous FHR monitoring. Fetal scalp pH and lactate measurements are still the reference method. The conclusions of the last meta-analysis on the RCTs of the use of the fetal electrocardiogram (STAN®) appear to be disappointing, because no differences were found in the rates of metabolic acidosis and the rates of cesarean deliveries. Intrapartum asphyxia’s diagnostic can be made by analysis of the acidbase status on the cord arterial blood. Therefore, it should be systematically performed after every births.     

Severe variable decelerations and fetal pulse oximetry during the second stage of labor

OBJECTIVES: The aim of the study was to investigate the usefulness of fetal pulse oximetry in cases of severe variable decelerations in the second stage of labor. METHODS: It is a prospective study including 58 patients. Thirty-eight patients (group A) had a normal uncomplicated labor and 20 patients (group B) developed severe variable decelerations during the second stage of labor. All patients were primiparous with normal pregnancies and had electronic fetal monitoring of labor in conjunction with fetal pulse oximetry. An estimation of fetal pH and base deficit was performed at delivery in all patients. RESULTS: There was no statistically significant difference in relation to maternal age and gestational age between the two groups. Group A patients did not delivered neonates with metabolic acidosis. Six out of 20 (group B) patients delivered neonates with a pH <7.10 despite a fetal pulse oximetry reading of >30%. CONCLUSIONS: It appears that fetal pulse oximetry is not capable of detecting pre-acidotic or acidotic fetuses during the second stage of labor in patients with severe variable decelerations and the management of such patients should be supported by fetal scalp pH when indicated or otherwise the obstetrician should expedite delivery either with assisted operative delivery or cesarean section. Fetal heart rate monitoring was introduced into clinical practice over 30 years ago. It continues to be the predominant method of intrapartum fetal surveillance despite worries about its accuracy and efficacy.     

Intrapartum Fetal Oxygen Saturation Monitoring in Congenital Fetal Heart Block

Summary: Conventional intrapartum electronic fetal heart rate monitoring is not informative in certain fetal conditions because the electronically-monitored fetal heart rate pattern is uninterpretable in terms of reflecting fetal normoxia. Such fetal conditions include various cardiac dysrrhythmias and some central nervous system abnormalities. Difficulties with intrapartum fetal welfare surveillance in such conditions often lead to operative delivery as a precautionary measure. We report 2 cases of intrapartum fetal oxygen saturation monitoring in the presence of congenital complete heart block (CCHB), using the Nellcor N400/FS14 oxygen saturation monitoring system. Mean intrapartum fetal oxygen saturation (FSpO₂) was 32% (SEM ± 1%) in the first case and 48% (SEM ± 0.3%) in the second case. In both cases, vaginal delivery of otherwise healthy infants was achieved. Fetal pulse oximetry is a promising new technique which directly measures fetal oxygenation without reference to fetal heart rate patterns. It may assist in the intrapartum fetal welfare assessment in conditions such as complete heart block, thereby helping to avoid otherwise unnecessary operative delivery.     

Problems with intrapartum fetal heart rate monitoring interpretation and patient management

Fetal heart rate (FHR) monitoring was introduced over 3 decades ago into clinical use and patient management. It continues to be the predominant method for intrapartum fetal surveillance despite questions about its efficacy and outcomes associated with its use. Currently, there appears to be a consensus regarding the reassuring value of a normal reactive pattern without decelerations. Patterns containing absent variability associated with persistent late decelerations, severe variable decelerations, and prolonged decelerations are generally believed to be ominous and may correlate with hypoxia of such severity that fetal central nervous system (CNS) damage may already have occurred. The clinician, however, is faced with FHR patterns between these extremes, and there appears to be a lack of consensus about their management. Furthermore, there is recent evidence that a fetal inflammatory response may lead to CNS damage, and the FHR patterns associated with this condition are not yet understood nor are there any intervention strategies that have been shown to benefit such fetuses. This article is an attempt to illustrate these situations and offer an approach useful to the clinician faced with such FHR patterns.     

Vibroacoustic and scalp stimulation

Both VAS and scalp stimulation are useful in the evaluation of fetal compromise by decreasing the number of falsely abnormal FHR tests and limiting the number of unnecessary interventions, thus improving the efficiency of antepartum and intrapartum FHR monitoring. As is true for all types of fetal assessment using FHR monitoring, VAS and scalp stimulation have limitations, and a lack of response to these methodologies does not necessarily indicate fetal acidemia. When either VAS or scalp stimulation is employed, one must take into consideration their respective predictive values (see Table 1). Fetal VAS or scalp stimulation should be considered as one facet of comprehensive fetal evaluation. When these techniques are used in this manner, the clinician evaluating the fetus in the antepartum or intrapartum period may prevent unnecessary intervention and improve maternal and neonatal outcome.     

Managing nonreassuring fetal heart rate patterns before cesarean delivery. Compliance with ACOG recommendations

OBJECTIVE: To determine the rate of compliance with current American College of Obstetricians and Gynecologists (ACOG) recommendations for management of parturients undergoing cesarean delivery for persistent nonreassuring fetal heart rate (FHR) tracings. STUDY DESIGN: We performed a retrospective chart review (July 1995-June 1998) of all parturients who underwent cesarean delivery for nonreassuring FHR tracings. Outcome measures included maneuvers for fetal assessment (scalp stimulation or scalp blood pH) and therapeutic interventions (tocolytic agents for reducing uterine activity or amnioinfusion). Patients with multiple gestations and cesarean delivery for other indications were excluded. Student's t test, chi 2 and Fisher's exact tests were used; odds ratio and 95% confidence interval were calculated. P < .05 was considered significant. RESULTS: Cesarean delivery for persistent nonreassuring FHR patterns included 134 (3.6%) of the 3,671 deliveries during three years. Thirty patients produced intrapartum FHR tracings containing persistent variable decelerations; 12 (40%) of these patients received amnioinfusion. In only 37% (50/134) of cases was there a documented attempt at scalp or acoustic stimulation prior to delivery. Scalp pH was obtained in 15% (15/98) of patients whose cervix was at least 3 cm dilated. Tocolytic agents were used for intrauterine resuscitation in 25% (34/134) of cases; their use varied significantly (P = .006) with the type of FHR abnormality. CONCLUSION: At our tertiary center, ACOG recommendations for management of nonreassuring intrapartum FHR tracings were used in a limited number of cases.     

Impact of abnormal results of outpatient fetal heart rate monitoring on maternal intervention in labor

OBJECTIVE: To conduct a retrospective, cohort study to determine the impact of abnormal outpatient fetal heart rate (FHR) testing on maternal interventions in labor, including labor induction, operative vaginal delivery and unplanned cesarean section. STUDY DESIGN: Our cohort consisted of 1,386 women with singleton gestations who had outpatient fetal nonstress testing within 1 week prior to giving birth etween 1993 and 1998. Antepartum FHR records were interpreted as reassuring or nonreassuring, and pregnancy records were abstracted for background medical information, labor interventions and pregnancy outcomes. Logistic regression models were used to describe the association between abnormal outpatient monitoring results and maternal interventions in labor. RESULTS: After adjusting for potential confounders (maternal age, race, prior history of cesarean section, antepartum indications for monitoring, fetal presentation and abnormal fetal heart rate patterns in labor), women with nonreassuring monitoring were 90% more likely to undergo induction. The 2 groups were similar in operative vaginal delivery rates, but pregnancies with nonreassuring testing were more than twice as likely to end with an unplanned cesarean section. CONCLUSION: Abnormal outpatient antenatal FHR testing may be independently associated with an increased risk of unplanned cesarean section.